Anesthesia & renal physiology- week 4 Flashcards
Normal ECF H+ is:
40nEq/L
Acid-base physiology is all about
H+ ion concentrations
a low pH corresponds to a:
high H+ concentration
Whats the normal pH or arterial blood?
7.4
what is the normal pH or venous blood and interstitial fluids
7.35
bc of the extra amounts of carbon dioxide released from the tissues for Carbonic acid (H2CO3)
acid is defined as a proton (H+)
donor
base is defined as a proton (H+)
acceptor
a weak acid or base reversibly
donates or accepts protons
What is the henderson-hasselbalch equation?
describes the relationship btwn pH, paco2, and bicarb
what is the solubility coefficient for Co2?
0.03 mmol/mmhg at body temperature
this means that 0.03 millimole of H2Co3 (carbonic acid is present in the blood for each mmHg Pco2 measurement
the HCO3- concentration is regulated mainly by:
the kidneys
The PCO2 in extracellular fluid is controlled by:
rate of respiration
WHen are buffers most efficient?
when pH= pKa
Solutions of ____ ____ or _____ act as ______ as they minimize pH changes by donating or accepting electrons
weak acids or bases act as buffers
What are the body buffers?
Bicarbonate (H2CO3/HCO3)
Hemoglobin
Intracellular proteins
Phosphate
Ammonia
buffer systems do not ______ or ______ ______ but only keep them tied up until balance can be restored
Buffer systems do not eliminate or Add H+
what are the 3 primary systems that regulate the H+ concentration in the body fluids to prevent acidosis or alkalosis?
1.) the chemical acid-base buffer systems of the body fluids (immediately combine w an acid or base to prevent excessive changes in H+ concentration)
2.) Respiratory center
3.) Kidneys - by far the most powerful acid-base regulatory system
what is the bicarbonate buffer system?
hydration of co2 is catalyzed by carbonic anhydrase
-pKa of bicarb is 6.1 (far from plasma pH)
-most powerful extracellular buffer in the body
What is the renal compensation during acidosis?
increased HCO3- reabsorption
-co2 combines w water to form carbonic anhydrase (H2CO3) which rapidly dissociated into H+ and HCO3-
-H+ is SECRETED into the proximal tubule and bicarb is reabsorbed into the blood
Where is H+ secreted into the tubular fluid by the sodium-hydrogen counter-transport?
PCT
TAL
DCT
80-90% of filtered bicarb is reabsorbed in the:
proximal tubule
10-20% of bicarb reabsorbed in the:
distal tubule
in the distal tubule a _____ ____ exists which can establish a steep gradient for acidifying urine
H+ pump
What is the phosphate buffer?
effective buffer in the tubular fluid
pKa of 6.8
- important buffering intracellular fluid bc the concentration of phosphate in this fluid is many times the extracellular fluid.
the intracellular fluid is lower than that of the extracellular fluids and therefor is usually closer to the pKa of the phosphate buffer system compared w extracellular fluid